Brief Description of the Prior Art
Due to enormous number of diverse applications, nozzle design is a fairly mature area of development with a wide variety of arrangements that have evolved over the years. Recently, sophisticated design techniques employing the latest test equipment and arcane mathematical algorithms for fluid dynamic modeling have imparted a new approach to nozzle design. Notwithstanding this design approach, the complexity of the system defies effective mathematical modeling and the design of nozzles remains more art than science--with heavy reliance on trial and error for advancing and fine tuning any given approach. Often the expected successful design fails while inexplicably simple variations thereof succeed.
Nozzles are used in different ways for different purposes; but all have in common the release of a high pressure fluid into a lower pressure environment. Of particular interest in the present discussion is the use of nozzles to provide a finely divided mist of water, i.e., in droplet form where the individual droplets are very small and uniform. The use of finely divided water droplets are of significant commercial value in gas cooling towers where a high temperature gas (2000.degree. Fahrenheit) must be rapidly cooled to approximately 200.degree.. Introducing a finely divided mist of water droplets into the gas stream causes the water to evaporate--almost instantaneously--soaking up heat energy via the phase change in the process and reducing the gas stream temperature dramatically.
However, gas cooling with a water droplet stream that comprises relatively large droplets creates secondary problems. The large droplets take significantly longer to evaporate and many simply don't. These residual droplets collect dust and other particulate matter in the gas stream and coalesce on the tower wall or floor, creating deposits that require separate cleaning and disposal. This maintenance can become a significant expense in the overall economics of the cooling process.
Most misting nozzles for gas cooling employ air as a propellant to the water, to increase discharge velocity and provide for enhanced disbursement of the individual droplets as formed. Air is supplied at about the same pressure as the water, and thus, must be pressurized via air compressors or similar--equipment that is both capital intensive per unit capacity and energy intensive. This leads to fairly high operating costs per unit capacity. Air is otherwise not an important component of the system, and thus, it is often a critical design criteria for nozzle designers to develop systems that minimize the amount of air required without diminished performance.
Another important aspect of the use of nozzles in gas cooling relates to their expected lifespan. Many gas cooling towers exist in a highly abrasive and/or corrosive environment as sulfuric acid and other corrosive gases invariably come in contact with the nozzles. To extend the life of the nozzles, the materials of construction will include specialized metals (e.g., hastalloys) or ceramics. These materials extend life and thus reduce maintenance, but are difficult to precisely machine. Moreover, the nozzles themselves must be disconnected, inspected and reinstalled to insure good long term performance. This inspection work is done in a nasty plant environment by semi-skilled personnel, with the potential for faulty reinstallation of the nozzle and ancillary equipment. Nozzle design, therefore, must consider the limitations associated in machining certain materials implicated by such environments and further provide a design that is easy to install without error or misconnection.
It was with the above understanding that the present invention was made.